In a commonly used type of electric meter, the meter housing is retained on the meter socket box by a clamping ring of U-shaped cross-section, which enclose the mounting ring of the meter and a mounting flange on the meter socket box. The ends of the clamping ring are turned radially outwardly (usually to extend downwardly), and a bolt is provided to draw the ends of the ring together to tighten the ring around the meter and base flanges.
Means must be provided for preventing unauthorized persons from loosening the ring to remove the meter to short across the terminals to by-pass the meter.
For example, in U.S. Pat. No. 4,008,585 there is illustrated a form of locking cover which has a side aperture aligned with apertures in the ends of the clamping ring, to receive a locking bolt of the so-called barrel lock type, as shown in U.S. Pat. No. 4,015,456. Although the housing illustrated in said U.S. Pat. No. 4,008,585 has achieved considerable commercial success, there are certain meter installations where it cannot be used because the lock is loaded into the housing from the side. In many meter installations in apartment houses, for example, where there is one meter for each apartment, the meters are often mounted to close together that there is not room enough for the barrel lock and operating key to be positioned between two adjacent meters.